1. Field of the Invention
The present invention relates to optical recording methods and media, and in particular, to a method for managing a defective area on a WORM-type optical recording medium, and an optical recording medium using the same. The method is particularly adapted for reproducing data recorded on write-once optical discs such as those using the recently developed Blu-ray disc format known as BD-WO.
2. Discussion of the Related Art
Data recording devices and media using optical read/write means have generally been categorized according to their writing capability or flexibility. Among read-only optical recording media, there are those using CD-ROM and DVD-ROM formats, which have no write capability. Among known disc standards that allow multiple write operations to be freely performed, there are CD-RW, DVD-RAM, DVD-RW, and DVD+RW types, which are rewritable compact discs and digital versatile discs.
WORM-type discs, on the other hand, are adopted for use as data storage devices requiring large storage capacity. Such discs, however, have limited recording flexibility and are for use in write-once read-many applications. These include CD-R and DVD-R types, which are recordable compact discs and digital versatile discs.
Meanwhile, a new type of high-density DVD, known as a Blu-ray disc, which is a large-capacity optical disc for recording high-quality audio and video data using a blue-violet laser, has been developed. The Blu-ray disc adopts a rewritable disc format known as BD-RE.
In the above types of optical recording media, surface imperfections and defects are generated during their manufacture, handling, or use. Accordingly, a method for managing the defective areas is used during a data recording operation, so that data reproduction can be carried out normally.
Referring to FIG. 1, an optical disc recording/reproducing device 100 for use with an optical recording medium 102, such as a BD-RE formatted disc, receives a data/ command input from a host (or controller) 200. The optical disc recording/reproducing device 100 is provided with an optical pickup 104 for writing/reading data to/from an inserted optical recording medium, a pickup servo 106 for controlling the optical pickup to achieve proper tracking and to maintain a controlled distance with respect to the surface of the optical recording medium, a data processor 108 for processing data to and from the optical pickup by restoring to a desired signal value a reproduction signal received from the optical pickup or by modulating a recording signal received from the host for transfer to the disc, an interface 110 for transferring data between the host and the recording/reproducing device, a microcomputer 112 for controlling the recording/reproducing device, and a memory 114 for storing a program and for temporarily storing various information including defect management information and data. Under the control of the host 200 and stored programming, the optical pickup 104 reads data stored (or written) on a disc, providing a data signal input to the data processor 108 for reproduction processing and output, and writes data onto specified areas of the disc using a write signal output from the data processor. During a write operation, the optical disc recording/reproducing device 100 receives a data stream (or an encoded analog signal) and outputs the write signal to the optical pickup 104 in accordance with a command input via the host 200 and the program stored in the memory 114 and executed by the microcomputer 112.
Referring to FIG. 2, a BD-RE type disc for use with the device of FIG. 1 is divided into assigned areas. The assigned areas essentially comprise a data area set between a lead-in area (LIA) and a lead-out area (LOA). The data area includes an inner spare area (ISA) adjacent the lead-in area and an outer spare area (OSA) adjacent the lead-out area.
As above, the optical disc recording/reproducing device 100 processes input data from a host 200 and writes the data onto an optical disc in clusters corresponding to an error correction code block unit. If during a write operation the existence of a defective area is detected in the data area, the optical disc recording/reproducing device 100 carries out a series of replacement write operations to write a data cluster corresponding to the detected defective area in one of the two spare areas (shown in the example of FIG. 2 as the ISA). Therefore, by writing a data cluster of a defective area in a spare area instead of the defective area, the data can be read and reproduced from the spare area, thus preventing the occurrence of writing errors even when an optical disc exhibits defects in the data area and thereby assuring data security and data integrity.
The above method is carried out using an optical recording medium that allows free access to the data recording areas, since a rewritable disc is used. Therefore, in managing the data of the defective areas, the optical disc recording/reproducing device has unlimited use of the recording area. If a WORM-type disc is used, however, the write operation is performed only once and must be completed before normal data retrieval operations by the user can be carried out. Moreover, write operations  and, in particular, replacement write operations—must be enabled for the management of defects generated after recording and detected during the reproduction of a recorded WORM-type disc.
For example, another type of Blu-ray disc, using a format known as BD-WO, has been recently developed. The BD-WO type disc, which is a write-once type disc, cannot make use of known methods for managing a defective area on the disc, since the standardization of this type of disc format has only recently begun. An immediate solution is required.